1. Field of the Invention
The present invention relates to a torque angle sensor and an electronic power steering apparatus having the torque angle sensor. More particularly, the present invention relates to a torque angle sensor and an electronic power steering apparatus having the torque angle sensor, which can remove a circumferential clearance and an axial circumferential clearance during assembling of the torque angle sensor with peripheral elements and can absorb movement created by an impact, so that it is possible to prevent breakage and mis-operation of the elements included in the torque angle sensor and to facilitate the assembling of the electronic power steering apparatus.
2. Description of the Prior Art
A vehicle generally uses a power steering apparatus serving as a means for reducing steering power of a steering wheel (handle) and guaranteeing stability of a steering state. In this respect, a conventional Hydraulic Power Steering system (HPS) using hydraulic pressure has been widely used for the HPS of the vehicle. However, in contrary to the conventional scheme of using the hydraulic pressure, an Electronic Power Steering System (EPS) that makes steering performance of a driver easy using rotational force of a motor and is environment-friendly has been widely installed in vehicles recently.
Such an EPS drives a motor by means of an electronic control unit according to a driving condition of a vehicle sensed in a vehicle speed sensor, steering angle sensor, steering torque sensor, or the like, so that it provides a light and comfortable steering sense in low-speed driving, a heavy steering sense and satisfactory direction stability in high-speed driving, and restoration force for promptly restoring the steering wheel according to a rotation angle of the steering wheel. Therefore, the EPS enables the prompt steering in an emergency so that it provides the driver with an optimum steering condition.
Meanwhile, in the EPS, the motor is installed in an external side of a steering column that is located between the steering wheel and a gear box so as to downwardly transfer the rotational force of the steering wheel of the driver so that it rotates a steering shaft within the steering column, thereby complementing steering power of the driver according to the steering of the steering wheel.
FIG. 1 is a view schematically illustrating a conventional electronic power steering apparatus. As shown in FIG. 1, the electronic power steering apparatus 100 includes a steering system 130 extending from a steering wheel 102 to wheels 126 in both sides and an auxiliary power mechanism 140 for supplying steering auxiliary power to the steering system 130.
The steering system 130 includes a steering shaft 106, of which one side is connected to the steering wheel 102 to rotate together with the steering wheel 102 and the other side is connected to a pinion shaft 108 through a pair of universal joints 104. Further, the pinion shaft 108 is connected to a rack bar 112 through a rack-pinion mechanism part 110 and both ends of the rack bar 112 are connected to the wheels 126 of a vehicle through a tie road 112 and a knuckle arm 124.
The auxiliary power mechanism 140 includes a torque sensor 142 for sensing torque applied to the steering wheel 102 by the driver and outputting an electric signal proportional to the sensed torque, an electric control unit 144 for generating a control signal based on the electric signal transferred from the torque sensor 142, a motor 146 for generating auxiliary power based on the control signal transferred from the electric control unit 144, and a reducer 150 including a worm gear 152 and a worm wheel gear 156 for transferring the auxiliary power generated in the motor 146 to the steering shaft 106.
Depending on the case, either the torque sensor 142 or the angle sensor 143 may be provided at one side of the worm wheel gear 156, or both of the torque sensor 142 and the angle sensor 143 may be provided at one side of the worm wheel gear 156, to construct the electronic power steering apparatus 100.
Recently, when the torque sensor and the angle sensor are assembled with the steering shaft, respectively, there is a problem in that the volume of the electronic power steering apparatus increases and the manufacturing cost and the assembling processes increase. In this respect, a torque angle sensor having the unified function of the torque sensor and the angle sensor has been developed.
However, the torque angle sensor having the unified function of the torque sensor and the angle sensor includes a lot of precision components, so that when the torque angle sensor is mounted to the steering shaft, the torque angle sensor creates problems of generating malfunction due to the clearance in a circumferential direction or an axial direction, or damaging the included components or generating malfunction due to even a light impact transferred from the outside.